fix: added error messages for passing oracles and references from unconstrained to constrained functions

compiler/noirc_evaluator/src/errors.rs

@@ -48,6 +48,8 @@ pub enum RuntimeError {
     BigIntModulus { call_stack: CallStack },
     #[error("Slices cannot be returned from an unconstrained runtime to a constrained runtime")]
     UnconstrainedSliceReturnToConstrained { call_stack: CallStack },
+    #[error("All `oracle` methods should be wrapped in an unconstrained fn")]
+    UnconstrainedOracleReturnToConstrained { call_stack: CallStack },
 }
 
 // We avoid showing the actual lhs and rhs since most of the time they are just 0
@@ -139,6 +141,7 @@ impl RuntimeError {
             | RuntimeError::NestedSlice { call_stack, .. }
             | RuntimeError::BigIntModulus { call_stack, .. }
             | RuntimeError::UnconstrainedSliceReturnToConstrained { call_stack } => call_stack,
+            RuntimeError::UnconstrainedOracleReturnToConstrained { call_stack } => call_stack,
         }
     }
 }

compiler/noirc_evaluator/src/ssa/acir_gen/mod.rs

@@ -612,9 +612,11 @@ impl Context {
                             self.ssa_values.insert(*result, output);
                         }
                     }
-                    Value::ForeignFunction(_) => unreachable!(
-                        "All `oracle` methods should be wrapped in an unconstrained fn"
-                    ),
+                    Value::ForeignFunction(_) => {
+                        return Err(RuntimeError::UnconstrainedOracleReturnToConstrained {
+                            call_stack: self.acir_context.get_call_stack(),
+                        })
+                    }
                     _ => unreachable!("expected calling a function but got {function_value:?}"),
                 }
             }

compiler/noirc_frontend/src/hir/type_check/errors.rs

@@ -120,6 +120,10 @@ pub enum TypeCheckError {
         "Cannot pass a mutable reference from a constrained runtime to an unconstrained runtime"
     )]
     ConstrainedReferenceToUnconstrained { span: Span },
+    #[error(
+        "Cannot pass a mutable reference from a unconstrained runtime to an constrained runtime"
+    )]
+    UnconstrainedReferenceToConstrained { span: Span },
     #[error("Slices cannot be returned from an unconstrained runtime to a constrained runtime")]
     UnconstrainedSliceReturnToConstrained { span: Span },
     #[error("Only sized types may be used in the entry point to a program")]
@@ -213,6 +217,7 @@ impl From<TypeCheckError> for Diagnostic {
             | TypeCheckError::OverflowingAssignment { span, .. }
             | TypeCheckError::FieldModulo { span }
             | TypeCheckError::ConstrainedReferenceToUnconstrained { span }
+            | TypeCheckError::UnconstrainedReferenceToConstrained { span }
             | TypeCheckError::UnconstrainedSliceReturnToConstrained { span } => {
                 Diagnostic::simple_error(error.to_string(), String::new(), span)
             }

compiler/noirc_frontend/src/hir/type_check/expr.rs

@@ -194,6 +194,17 @@ impl<'interner> TypeChecker<'interner> {
                     return Type::Error;
                 }
 
+                // Check that we are not passing a reference from an unconstrained runtime to a constrained runtime
+                if is_current_func_constrained
+                    && is_unconstrained_call
+                    && matches!(&return_type.follow_bindings(), Type::MutableReference(_))
+                {
+                    self.errors.push(TypeCheckError::UnconstrainedReferenceToConstrained {
+                        span: self.interner.expr_span(expr_id),
+                    });
+                    return Type::Error;
+                }
+
                 return_type
             }
             HirExpression::MethodCall(mut method_call) => {

test_programs/compile_failure/unconstrained_oracle/Nargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "unconstrained_oracle"
+type = "bin"
+authors = [""]
+[dependencies]

test_programs/compile_failure/unconstrained_oracle/src/main.nr

@@ -0,0 +1,9 @@
+#[oracle(getNoun)]
+unconstrained fn external_fn() -> Field {
+    100 / 5
+}
+
+fn main() {
+    let x = anon();
+    assert(x * 5 == 100);
+}

test_programs/compile_failure/unconstrained_ref/Nargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "unconstrained_ref"
+type = "bin"
+authors = [""]
+[dependencies]

test_programs/compile_failure/unconstrained_ref/src/main.nr

@@ -0,0 +1,8 @@
+unconstrained fn uncon_ref() -> &mut Field {
+    let lr = &mut 7;
+    lr
+}
+
+fn main() {
+    let e = uncon_ref();
+}

test_programs/compile_failure/unconstrained_slice/Nargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "unconstrained_slice"
+type = "bin"
+authors = [""]
+[dependencies]

test_programs/compile_failure/unconstrained_slice/src/main.nr

@@ -0,0 +1,11 @@
+unconstrained fn uncon_slice() -> [Field] {
+    let mut slice: [Field] = [0; 2];
+
+    let mut new_slice = slice.push_back(6);
+    new_slice
+}
+
+fn main() {
+    let e = uncon_slice();
+    e
+}